Please click here to visit the "Military Rifle Components Guide" for
additional info and photos of the various components used on this model.
HISTORY / BACKGROUND:
The Colt Model 603 / XM16E1 was the first attempt at providing an improved M-16 for the US Army. The Colt
Model 603 / US Army XM16E1 production ran from early 1964, and transitioned into the Colt Model 603 / US
Army M16A1 in early 1967.  It was the first model to incorporate the forward assist feature. This model was
also one of the first to use the "Partial Fence" reinforced lower receiver. This was a "transitional" model and
as such early and late models could have been found with varying component makeups.
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BUTTSTOCK:
STYLE:
Later / Improved Solid Body
Type D


BUTTPLATE:
Solid Rubber



SWIVEL:
Pinned, Metal with
Plastic Covering


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BUFFER GROUP:
BUFFER:
"Original" Edgewater Design


SPRING:
Standard Rifle Spring


TUBE:
Original Tube,
No wrench flats,
Hole in tube at receiver
end to tighten tube

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LOWER RECEIVER:
STYLE:
"Partial Fence"


MARKINGS:
Colt Logo
COLT AR-15
PROPERTY
OF U.S. GOVT.
XM 16 E1
CAL. 5.56 MM.
Serial XXXXXX


SELECTOR:
"Later"


TAKEDOWN / PIVOT PINS:
"Later" Pins


BOLT CATCH/RELEASE:
"Latter" with Raised/Grooved End

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UPPER RECEIVER:
PROOF MARKS / FORGE CODE:
Colt Proof Marks - Triangle & Square with "C"
Located in front of ejection port
No Forge Code


REAR SIGHT:
Raised Directional Markings on Receiver


EJECTION PORT COVER:
"Later" with " Rectangular Plate"
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BOLT GROUP:
CARRIER:
Early - Chrome with
Forward Assist Serrations
Late - Parkerized with
Forward Assist Serrations

BOLT:
Early - Chrome
Late - Parkerized

FIRING PIN:
Improved Light Flat Head

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CHARGING HANDLE:
Current Improved Design







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HANDGUARD SLIP RING:
Flat





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BARREL:
DIAMETER:
0.625" at the Front Sight Base

LENGTH:
20"

TWIST RATE:
1/12

MARKINGS:
Colt Proof Marks
Between FSB Legs

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HANDGUARDS:
Standard Triangular




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FRONT SIGHT BASE:
STYLE:
Early - Cast
Late - Forged, with flash removed


MARKINGS:
Unmarked








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FLASHHIDER:
Early - Improved 3 Prong Flashhider




Late - A1 Birdcage
Unknown Date - Vietnam
US Navy SEAL
Unknown Date - Vietnam
US Army LRRP
RETRO BLACK RIFLE - RIFLE GUIDE - MODEL 603 / XM16E1
Unknown Date - Vietnam
US Army
Unknown Date - Vietnam
With Colt 3 x 20 Scope
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ADDITIONAL COLT MODEL 603 / XM16E1 INFORMATION
US Army
setstats
.223 Cal / 5.56mm
MILITARY RIFLE
GUIDE
Military Rifle
Components Guide
Colt Model 601
Colt Model 602
Colt Model 603 /
XM16E1
Other M16A1
Manufacturers
Colt Model 604 /   
USAF M16
Colt Model 603
M16A1
Colt Model 606
HBAR
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